Air preheater for furnaces and the like



M. STEUE RMAN AIR PREHEATER FOR FURNACES AND THE LIKE Get. 15, 1946.

5 Sheets-Sheet 1 Filed' Jan. 8. 1944 Inventor MAREK smusmmw F Atlorney Oct. 15 1946. STEUERMAN 2,409,451

AIR PREHEATER FOR FURNACES AND THELLIKE' Fi led Jan. 8. 1944 3 Sheets-Sheet .2

Inventor MARE ST'EUERMAN A M Attorney 0d. 15, 1946. M, STEUERMAN 2,409,451

AIR PREHEATER FOR FURNACES AND THE LIKE Filed Jan. 8. 1944 3 Sheets-Sheet s I v Inventor V v AREK s-rzusnmu By L Attorney Patented Oct. 15, 1946 OFFICE AIR PREI-IEATER FOR FURNACES AND THE LIKE Marek. Steuerman, London, England Application January 8, 1944; Serial No.517,601 In Great Britain March. 26,1942

4 Claims.

This invention concerns air preheaters for furnaces and the like. of the kind adapted to be mounted on the inside or the fire door or in any other suitable convenient position for the purpose of preheating air passing into the furnace above the fire grate with the object of obtaining improved combustion of the fuel on such grate, such preheaters each comprising a hollow body adapted to be heated by the fire in the furnace and constrcted so that air, or some air, on its way into the furnace may pass through the pre'. heaterand be preheated prior to entering the firespace.

An object of this invention is to'provide an improved. form? of air preheater, and according to the invention there is provided an airpreheater of'the kind referred to for furnaces and the like, wherein within the hollowbody, and behind the front wall (i. e., the wall presentedzto the fire) thereof, is arranged a flap or partition. dividing the hollow body into two compartments, such flap or partition being movable towards and away from the said front wall to. control the flow of air through the space between the front wall of the hollow body and the such flap or partition, and wherein means are, also provided for adjusting the position of such. flap or partition preferably from the exterior of the hollow body.

Moreparticularly the invention is concerned with air preheaters of the kind referred to and in which 'baflle means are provided within the hollow body to ensure that the air to be preheated will take a tortuous path through the hollow body; Therefore, according to a further feature of the invention baflie means arearranged between the said movable flap or partition and the said front wall of the hollow body to'define one or more tortuouspaths to which theair passing through the space between the front wall of the hollow body and the movable flap or partition must, pass. Preferably the said baflle means are constituted by co-operating interleaved baffles carried respectively upon one surfaceof the said movable flap. or. partition. and on the. opposite insidesurface ofrthersaid front wall of the hollow body.

Pref era'bly, buti'not necessarily, the-arrangement of'the said'bafile means is such that the air to be preheated passes tortuouslybackwards and forwards in the. hollow body (i. e. transversely of thesaid movable flap or partition and the front'wall of the hollow body), the air preferably enteringthetortuouspath" provided by the bafile means at or; near the lower part" of. the hollow body, gradually rising to, and. leaving the tor- 2 tuous path at or near the upper part of the hollow'body. .After leaving this tortuous path the air may be discharged directly into the furnace through one or more openings .in the front Wall 5 and/or top and/or ends of the hollow body or in any other suitable way, or a supplementary or superheating chamber may be provided at the upper portion of V the preheater, which chamber may project forwardly beyond the frontfa ce of the front wallof the hollow body, and which may have. a rectilinear; curved, or otherwise suitably shaped front wall in which isor arearranged one or more discharge apertures.

The arrangement is preferably such that air is admitted into the space between the movable flap or partition and the front wall of the hollow body through a gapbetween these two parts, the closing or opening of the said gap, and the extent to which itis opened being obtained and regulated by adjusting the movable fiapor partition'with respect to the front wall of the hollow body. Preferably said gap is provided at the lower part of the hollow body and. is constituted on the one hand by alongitudinal seat formed upon the inside of the front wall-of the hollow body, and on the other hand by the front surface of the adjustable flap or partition which is adapted, in the closed position of the flap or partition, to seat upon the saidseat, thus closing 30, the gap entirely. Assuming the preheater to be set with its rear Wall vertical, the said longitudinal seat, which is preferably horizontal, is convenient ly disposed at a; shbrt distance from the bottom of the hollow body and at a location intermediate the front wall and the back of the hollow body, and the said movable flap or partition preferably extends from end to end of the hollowbody and from the top thereof to a position somewhat below the said seat so that the movable flap or 40 partition, with the said sea-t, separates the said two compartments of the hollow body from one another, aslot-like portion being left, however, adjacent the bottom ofthe hollow body so as to serve as an air inlet for the entry of air into the hollow body" and to the said regulatable gap between the movablerflap or partition and the said seat on the front wall, Alternatively,.the said adjustable flap or partition may extend to the" bottom of the hollow body and be provided with a hole or holes for the'passage of air therethrough at positions below the seat of the front wall.

Preferablythe frontzwall of the hollow body is formed internally with a.- series of side by side pa allelbutisomewhat spaced channels arranged one above the other and extending longitudinally of the hollow body, and between these channels are arranged the hereinbefore mentioned baflies which exend parallel to the channels and backwardly from the said front wall. Similarly the front side of the said movable flap or partition is correspondingly formed, but the channels and bafiles of this flap or partition are offset with respect to those of the front wall, so that the bafiles of the flap or partition project more or less centrally into the channels of the front wall, and vice versa.

The front surface of the front wall may be ridged or corrugated to increase its area and so to increase the heat exchange surface thereof. Conveniently this front surface of the front wall of the hollow [body is corrugated or ridged longitudinally, the crests of the corrugations follow,- ing in shape, and coinciding in position with, the bottoms of the channels in the rear side of the front wall, which bottoms are preferably of semi-cylindrical form (i. e., semi-circular in cross-section). Thus the front surface of the front wall of the hollow body will appear to be made up of a series of parallel side by side superposed strips or bars, the front surface of each of which is of part cylindrical form. The channels and baflies of the said flap or partition may be shaped and arranged similarly to those of the front wall of the hollow body and the battles of both the latter and the said flap or partition may taper towards their free longitudinal edges.

A back plate may be provided to close the rear of the hollow body, or instead of using a back plate the furnace door may be relied upon to effect the closing of the rear of the hollow body. If, however, a back plate is used, then it is provided with one or more air inlet openings. Such inlet opening or openings may be at any suitable position and of any convenient shape and size, but preferably a single opening is provided at the lower part of the back plate, this opening being of elongated slot-like form extending al most from end to end of the plate and having its upper edge coinciding with the lower edge of the said movable flap or partition.

Preferably the front wall of the hollow body is backwardly and downwardly inclined with respect to the plane passing through the rear edges of the walls of the preheater, so that, regarding the preheater in end elevation, it appears to decrease in depth (from front to back) in a direction from the top towards the bottom, i. e. it is of wedge shape in end elevation.

Preferably the said movable flap or partition is pivotally mounted at its upper end in the hollow body, and screw and nut means are preferably provided on or near its lower end for adlusting the flap or partition, the screw part of the adjusting means being extended so as to project rearwardly of the preheater and being adapted to pass through the furnace door and to be provided with a handle or knob at its outer end so that the required adjustments may be made from the exterior of the furnace.

In order that the invention may be thoroughly understood and readily be carried into practice, drawing are appended hereto in which:

Figure 1 is a front elevation of one form of preheater constructed according to this invention;

Figure 2 is an end elevation of the same;

Figure 3 is a section on line 3--3, Figure 1;

Figure 4 is a back elevation of the preheater shown in Figures 1 to 5 partly broken away in successive sections to expose otherwise hidden parts of the interior construction of the preheater;

Figure 5 is a section on line 5-5, Figure 4; and

Figure 6 is a perspective view of the flap or partition in the interior of the preheater.

The air preheater illustrated in the drawings is intended to be attached to the inside of a furnace door. The preheater comprises a hollow body I of rectangular form as seen from the rear. From back to front it is relatively shallow as compared with its length and breadth and its front wall 2 inclines backwardly and downwardly slightly so that it is rather nearer the rear of the hollow body at the bottom thereof than it is at the top.

At its upper end the front wall 2 is externally and internally extended forwardly at 3 so as to provide a longitudinal forwardly extending chamber 2. The front wall 5 of this chamber is rectilinear and parallel to the back edge of the top wall 6 of the hollow body, but the said front wall could be curved, e. g., convex, or inclined forwardly from its ends towards its centre if desired. The wall 5 is provided with a row of air discharge openings 7 which are conveniently circular in cross-section and of frusto conical form, the narrower ends of the holes being their forward ends. The axes of the holes may be horizontal or somewhat downwardly inclined and they may or may not be parallel as seen in plan; for example, the axes of the holes as seen in plan may splay outwards somewhat in the manner of the thumb and finger of an extended hand, or they may converge towards one another in a forward direction. Except for the discharge holes above mentioned the front of the hollow body is entirely closed.

The bottom wall 8 of the hollow body is of a sinuous or ogce form in cross-section, so that inside the hollow body the bottom is on two levels, that is to say, the bottom consist of two longitudinal horizontal steps, a lower rear step 9 and a higher forward step I 0 separated by a substantially vertical longitudinal part or riser II. The rear edge of the said forward step is provided with a backwardly directed ridge or flange I2 which extends from end to end of the hollow body and overhangs the more or less vertical part or riser II. This backwardly directed ridge or flange l2 constitutes a seat upon which is adapted to sit, in certain circumstances, the lower part of a hinged flap or partition l3 subsequently to be more fully described.

Between the part of the bottom wall 8 of the hollow body and the bottom wall M (which wall also serves as a baffle) of the said chamber 4, and within the hollow body, are arranged a plurality of longitudinal parallel preferably equally spaced bafiies 5 which are formed in one with the in-' side surface of the front wall 2 of the hollow body and extend from end to end of the latter, parallel to the bottom 8 of the hollow body and backwardly from the said front wall 2 so as to have their rear edges substantially flush with the rear edge of the said longitudinal seat ID. This rear seat edge, and the rear edges of all the above-mentioned baflles, are spaced some distance from the plane containing the rear edge of the top and bottom walls 6 and 8 and the side walls l6 and ll of the hollow body, and since the baflles l5 are preferably all of the same width from back to front as one another, and as the front wall 2 of the hollow body inclines "downwardly towards the back of the hollow body, the rear edges of the baflles are consequently spacdprogressively further away from-the said and-between the topbaffie l5 and the lower wall "l4- of the said chamber ly is shaped to substantially semi cylindricalconcave formas seen from the back,-andthe outer front surface of-the front wall '2' is correspondingly shapedso that the front wall of -the hollow body has-a plurality of longitudinal; parallelconvex ribs I9 projecting therefrom; the longitudinal grooves r depressions 2i] between which ribscorrespond in position with thebafiles within the hollow body. Additional rib-s; fins, corrugations or projections may be provided on the hollow body if desired further to increase'the area ofthe heat exchange surfaces. The iront wall 2 also has a flattened portion 39 on which may be carriedthe makers name or otherdata- The hinged flap or partition l3 above referred to is disposed within the hollow body I, and comprises a rectangular'plate which is of a length substantially equal to the distance between the inside surfaces of the two end walls 16 and I! of the hollow body, but which plate is of a, depth from top to bottom somewhat less than the depth of the hollow body from top to bottom at the rear theref.

Adjacent its upper edge, the said plate is provided with a rib 2i carrying a trunnion 22 at each end (Figure and each of these trunnions seats in a bearing 23 (Figure 4) provided at the adjacent end wall of the hollowbody, and the trunnion is rotatably secured in that position by a cover piece 24 recessed into the back edge of the end wall of the hollow body and secured in position by one of the screws used to secure the back cover plate 25 (subsequently to be described) in position. When hinged in the hollow body I the upper edge of rib 2! of the flap or partition [3 lies adjacent the inside surface of the top wall 6 of the hollow body.

On its inner side the flap i3 is provided (see Figure 6 in particular) with a plurality of equally spaced parallel longitudinal baffles 26 which are preferably cast integrally with the plate, the plate, in cross-section, being of semi-cylindrical form between each pair of bailles as shown at 21. The baffles 25 on the flap is are similar to the baffles IE on the inside of the front wall 2 of the hollow body I, but when the hinged plate is in position in the hollow body, the bafiies 26 of the flap are offset with respect to the baffles IE on the hollow body so that the latter baffles project into the spaces between the baffles on the flap. However, the baffles on the movable flap and those on the front wall of the hollow body are preferably of such dimensions that the baffles on the one part never touch the bottoms of the grooves between the baffles of the other part,

The flap l3 projects downwardly below the lowermost baffle 26 on the plate so as to provide a longitudinally extending dependent flange 2B which is adapted, in the closed position of the flap, to seat upon the hereinbefore mentioned seat 12, provided on the hollow body, so as to prevent the ingress of air to the space 29 between the inner surface of the front wall 2 of the hollow body and the frontsurface of the hinged flap. Thus the cooperating parts -|2 and"23 act as'a form of valve. I

On the back ofthe hollow body is secured,-by screws, the metal back cover plate which is formed of metaland which has a portion of elongated rectangular form cut out of its lower edge to form an air inlet opening 30 opposite the space between the bottom edge of the said hinged flap i3 and the lower and rearmost step-like part 9 of the bottomt of the hollow body.

For the purpose of adjustingthe hinged flap i3 towards and away from the front wall 2 of the hollow body, a, screwed stem 3 I is provided which is mounted for rotatory, but non-axial, movement in a sleeve-32 screwed into the back plate 25 at the lower part of, and perpendicularly to, the-latter. The said sleeve is adapted to pass through the furnace door, and the sleeve and screwed stem are of such a length as to be capable of projecting beyond the outer side ofthe furnace door whilst the stem 3i also extends into the hollow body land into the said hinged'flap +3: The outer endof the screwed stem 3| is'provid'ed with a knob 33 for rotating it, and at its inner end thewstem is screwed into a nut- 35 which is housed inanon-rotatable mannerin a recess 36 provided at the-lower central part of the hinged'fiap I3 and closed by a Plate 31;

Preferably the top, bottom and side or end walls of the preheater slope inwardly towards the front wall thereof.

In use the preheater is fixed, for example by studs 38 within the furnace, for example fiat against the inside surface of the furnace door to the outside thereof so that the knob 33 can be manipulated from the outside of the furnace. The gap 30 at the lower part of the preheater is registered with a corresponding gap or with one or more air inlet holes provided in the furnace door.

The front wall 2 of the preheater is therefore presented in a somewhat oblique position to the fire within the furnace and in operation air enters through the gap 30 and rises within the preheater between the part 28 of the flap or partition l3 and the seat l2 and then passes in a tortuous backward and forward manner up through the preheater into the forwardly projecting chamber 4 and eventually out of the discharge holes I in the upper forwardly projecting portion or bulge 5 of the preheater, the air so leaving the preheater being directed towards the fire.

If the discharge holes 1 are arranged with their axes downwardly inclined then the streams of air issuing from these holes will be biased in a downward direction. The flow of air through the preheater is regulated by adjusting the flap or partition i3 to and away from the front wall 2 of the preheater by means of the adjusting screw 3! and the associated parts, this screw being operated by the knob 33 from the exterior of the furnace. If desired, the intake of air can be entirely shut off by adjusting the flap or partition l3 so that the part 28 thereof bears against the seat I2.

I claim:

1. An air preheater for furnaces and the like comprising a hollow body, its top wall being substantially imperforate, its rear wall being provided adjacent its bottom edge with air inflow means, the rear wall being otherwise substantially imperforate, the front wall of said hollow body being provided with air outflow means adjacent its upper edge, the front wall being otherwise substantially imperforate, the inner face of the front wall being provided with baflle-like formations extending generally in like directions and transversely to the direction from said air inflow means to said air outflow means; a plate disposed within said hollow body intermediate the inner plate being disposed alternately with respect to the free edges of said baffle-like formations of said front wall; means for pivotally mounting said inwardly disposed plate at its upper portion; and means extending through said rear wall for adjusting the pivotal position of said in wardly disposed plate.

2 An air preheater pursuant to claim 1 in which said bafile-like formations at the inner face of the front wall and said baflle-like formations of said inwardly disposed plate extend mutually in parallel directions.

3. An air preheater pursuant to claim 1 in which said baffle-like formations at the inner 8 face of the front wall and said baflie-like formations of said inwardly disposed plate extend mutually in parallel directions and substantially at right angles to the direction from said air inflow means to said air outflow means.

4. An air preheater for a furnace or the like, comprising a hollow box-like body, such body including a rear wall provided with air inlet means at its lower part and including a front wall having air discharge means at its upper part, a flap mounted within said body between said front and rear walls and pivotable about its upper end, means operable from the exterior of said rear wall for moving the lower end of said flap towards or away from said front wall, a shoulder on said front wall co-operating with the lower end of said flap to form a variable air inlet to the space between the flap and the front wall, a plurality of bafiles on said front wall projecting into said space between the flap and front wall, the parts of the rear face of said front wall between said bailles being of semi-cylindrical form, a plurality of baffles on said flap, such bafiles extending towards said front wall and being offset relatively to the baflies on said front wall, and the parts of the front face of said flap between the bafiles thereon being of semi-cylindrical form.

MAREK STEUERMAN. 

